"We have robust agreements in place to protect our members as much as possible during these difficult times. However, we remain vigilant and we are keeping a close eye on developments in the car industry."

Unite said the extended shutdown of Mini production would not affect workers' pay.

A spokeswoman for Mini said the last shift at Swindon will be on December 7 and the factory will remain shut until January 5.

The company said it was weathering the current economic slump "reasonably well", with worldwide sales up 12% this year, but the firm was not immune to the slowdown in the UK.

The longer shutdown will mean that 9,000 fewer Minis will be produced. Workers will continue to receive their basic pay and bonuses although some premium shift payments will be hit.